In any system in which multiple users demand attention from a limited resource, the system must be capable of handling scenarios in which the users simultaneously ask for more than the system can deliver. One way of dealing with potential log jams in such a system is to implement queues that cause each requested transaction to be handled in turn. First-in first-out (FIFO) and first-in last-out (FILO) are common queue implementations, in which transactions are handled either in the order in which they are received (FIFO) or from most newest to oldest (FILO). Although these queue implementations have the effect of handling transactions in turn, they do not have the ability to examine the details of the transaction being requested to more efficiently handle a queue, or to take transactions out of the normal queue order in a systematic fashion that improves the performance of the system.